The present application is directed to spinal stabilization devices and methods and, more specifically, to devices and methods that provide for asymmetrical vertebral motion in first and second directions.
The spine is divided into four regions comprising the cervical, thoracic, lumbar, and sacrococcygeal regions. The cervical region includes the top seven vertebral members identified as C1-C7. The thoracic region includes the next twelve vertebral members identified as T1-T12. The lumbar region includes five vertebral members L1-L5. The sacrococcygeal region includes nine fused vertebral members that form the sacrum and the coccyx.
The vertebral members provide for movement in various directions. The movement may include flexion, extension, lateral bending, axial rotation, or a coupled combination of these movements. In a normal spine, more motion occurs in a first direction than in a second direction. By way of example, the vertebral members may provide for greater flexion than extension.
Various conditions may lead to damage of the vertebral members and/or intervertebral discs. The damage may result from a variety of causes including a specific event such as trauma, a degenerative condition, a tumor, or infection. Damage to the intervertebral discs and vertebral members can lead to pain, neurological deficit, and/or loss of motion. Vertebral rods may be implanted to redistribute stresses and/or restore proper alignment of the vertebral members. The rods extend along a section of the spine and may include a curved configuration to conform to the curvature of the spine. The rods may provide for motion of the vertebral members.